The present invention relates to a pickup transducer or sensor for measuring forces and torques, which is remarkable as a result of its small overall dimensions and its modular character. The invention also relates to a follower or feeler and to a gripper using one or more pickups of this type.
In technical fields such as robotics and remote handling, it is often necessary to know the contact torsor between two solid objects. This is more particularly the case during the gripping of an object by a force return remote manipulator or by a robot. The knowledge of the contact torsor is also desirable in order to realize the insertion of an object into a part or when a follower has to follow the contour of an object with contact.
Most existing force and torque measuring pickups are wrist pickups placed at the end of the carrier supporting the gripper. These pickups normally make it possible to determine the forces exerted in three orthogonal axes and the moments of the torques about said three axes. Numerous models exist, reference being made e.g. to that of U.S. Pat. No. 4,094,192.
However, such wrist pickups have a number of disadvantages limiting the use thereof. Firstly they all have large overall dimensions, particularly in an orthogonal plane about their longitudinal axis of symmetry. Consequently the dimensions of these pickups cannot be sufficiently reduced to enable them to be directly placed in the fingers of a gripper. The wrist pickups thus make it possible to obtain information on the overall interaction between the gripper and the object to be gripped, but not the contact torsor between each of the fingers of the gripper and said object. Thus, the applications of such pickups are limited. Finally, such wrist pickups are generally sensitive to heat or are designed in such a way that the decoupling between the three forces and the three torques measured is difficult and requires very complex calculations.
Moreover, within the scope of very particular applications, certain force and torque measuring pickups have been designed so that they can be placed in the fingers of a gripper. However, these pickups are generally only sensitive to the forces and torques in one or two axes and they never make it possible to know the complete interaction torsor between each finger of a gripper and the object to be gripped. Thus, French patent application No. 2 520 279 describes a device making it possible to determine a force and two torques for each of the fingers of the gripper.
French patent No. 2 375 962 describes a gripper with two fingers, each having three plates located in orthogonal planes and operating in flexion, each plate being equipped with strain gauges. However, only three measurements are performed on each of the fingers, which in practice limits the applications of said device to the same cases as for the wrist pickups.